Dental appliance for treatment of snoring and obstructive sleep apnea

ABSTRACT

A dentally retained intra-oral appliance worn at night for treatment of snoring and obstructive sleep apnea. The appliance maintains the patient&#39;s mandible in an anterior, protruded position to prevent obstruction of the pharyngeal airway. The appliance allows a limited degree of lateral movement of the mandible relative to the upper jaw in the protruded position to prevent aggravation of the patient&#39;s tempromandibular joint and associated muscles and ligaments. The appliance preferably consists of an upper bite block conforming to the patient&#39;s maxillary dentition, a lower bite block conforming to the patient&#39;s mandibular dentition, and a connecting assembly secured to an anterior region of the upper and lower bite blocks for adjustably coupling the upper and lower bite blocks together.

This application is a continuation of application Ser. No. 08/554,670filed Nov. 8, 1995, now U.S. Pat. No. 6,041,784, which is a continuationof application Ser. No. 08/220,304 filed Mar. 30, 1994, now abandoned,which is a continuation-in-part of application Ser. No. 08/046,549 filedApr. 13, 1993 which issued as U.S. Pat. No. 5,365,945 on Nov. 22, 1994.

FIELD OF THE INVENTION

This application relates to a dentally retained intra-oral applianceworn at night for treatment of snoring and obstructive sleep apnea. Theappliance maintains the patient's mandible in an anterior, protrudedposition to prevent obstruction of the pharyngeal airway. The applianceallows a limited degree of lateral movement of the mandible relative tothe upper jaw in the protruded position to prevent aggravation of thetempromandibular joint and associated muscles and ligaments.

BACKGROUND OF THE INVENTION

Snoring and obstructive sleep apnea are typically caused by complete orpartial obstruction of an individual's pharyngeal airway during sleep.Usually airway obstruction results from the apposition of the rearportion of the tongue or soft palate with the posterior pharyngeal wall.Obstructive sleep apnea is a potentially lethal disorder in whichbreathing stops during sleep for 10 seconds or more, sometimes up to 300times per night. Snoring occurs when the pharyngeal airway is partiallyobstructed, resulting in vibration of the oral tissues duringrespiration. These sleep disorders tend to become more severe aspatients grow older, likely due to a progressive loss of muscle tone inthe patient's throat and oral tissues.

Habitual snoring and sleep apnea have been associated with otherpotentially serious medical conditions, such as hypertension, ischemicheart disease and strokes. Accordingly, early diagnosis and treatment isrecommended. One surgical approach, known as uvulopalatopharyngoplasty,involves removal of a portion of the soft palate to prevent closure ofthe pharyngeal airway during sleep. However, this operation is notalways effective and may result in undesirable complications, such asnasal regurgitation.

A wide variety of non-surgical approaches for treating sleep disordershave also been proposed including the use of oral cavity appliances. Ithas been previously recognized that movement of the mandible (lower jaw)forward relative to the maxilla (upper jaw) can eliminate or reducesleep apnea and snoring symptoms by causing the pharyngeal air passageto remain open. Several intra-oral dental appliances have been developedwhich the user wears at night to fix the mandible in an anterior,protruded (i.e. forward) position. Such dental appliances essentiallyconsist of acrylic or elastomeric bite blocks, similar to orthodonticretainers or athletic mouthguards, which are custom-fitted to the user'supper and lower teeth and which may be adjusted to vary the degree ofanterior protrusion.

U.S. Pat. No. 4,901,737, which issued to Toone on Feb. 20, 1990,exemplifies the prior art. Toone discloses an intra-oral appliance forreducing snoring which repositions the mandible in an inferior (open)and anterior (protrusive) position as compared to the normally closedposition of the jaw. Once the dentist or physician determines theoperative “snore reduction position” for a particular patient, anappropriate mold is taken of the maxillary dentition and of themandibular dentition for formation of the appliance template. The Tooneappliance includes a pair of V-shaped spacer members formed from dentalacrylic which extend between the maxillary and mandibular dentition toform a unitary mouthpiece. In an alternative embodiment of the Tooneinvention, the spacer members are formed in two pieces and a threadedrod is provided to enable adjustment of the degree of mandibularprotrusion or retrusion after the mouthpiece is formed.

European patent application No. 0,312,368 published Apr. 19, 1989 alsodiscloses an intra-oral device for preventing snoring. This deviceconsists of a U-shaped mouthpiece which conforms to the upper dentalarch of the user and includes a sloped, lower ramp for engaging themandibular dentition. Normal mouth motions, such as the clenching of thejaw, will cause some of the mandibular dentition to engage the undersideof the ramp, thereby camming the lower jaw forward to increase thespacing between the base of the tongue and the posterior wall of thepharynx.

While prior art dental appliances have proven effective in maintainingthe mandible in a protruded position to improve airway patency, theyoften result in undesirable side effects. One of the most common sideeffects is aggravation of the tempromandibular joint and related jawmuscles and ligaments, especially in individuals who have a tendency togrind their teeth during sleep. Aggravation of the tempromandibularjoint has been associated with a wide variety of physical aliments,including migraine headaches. Accordingly, many individuals sufferingfrom sleep apnea and snoring disorders are not able to tolerate existinganti-snoring dental appliances for long periods of time.

The need has therefore arisen for a dental appliance for treatment ofsnoring and sleep apnea which will maintain the mandible in a preferredanterior position, but which will also allow a limited degree of lateralexcursion of the mandible relative to the upper jaw to avoid discomfortto the tempromandibular joint and related muscles and ligaments.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided an intra-oral dentalappliance to be worn by a patient during sleep for treatment ofobstructive sleep apnea and snoring. The dental appliance includes anupper member conforming to the patient's maxillary dentition, a lowermember conforming to the patient's mandibular dentition, and connectingmeans for releasably coupling the upper and lower members together tomaintain the lower member in an anterior, protruded position relative tothe upper member. The connecting means includes adjusting means which ismanually adjustable to incrementally vary the degree of anteriorprotrusion of the lower member relative to the upper member. Theconnecting means is loosely coupled to the lower member to permit alimited degree of lateral movement of the lower member relative to theupper member in the anterior, protruded position.

The upper and lower members are preferably flexible bite blocks formedfrom elastomeric material. Preferably the connecting means is secured toanterior regions of the upper and lower bite blocks and includes a firstelement bonded to an undersurface of the upper bite block; a secondelement bonded to an upper surface of the lower bite block; and anelongated connector for releasably coupling the first and secondelements together.

Preferably the connector has an upper end which is fixedly connectableto the first element and a lower end which is loosely connectable to thesecond element to permit the limited degree of movement of the lowerbite block relative to the upper bite block in the protruded position.Advantageously, the second element has an internal cavity for capturingthe lower end of the connector, the cavity having an opening formed onan upper surface of the second element through which the connectorextends. The connector preferably consists of a stylus having a threadedupper portion and an enlarged head formed on its lower end having adiameter exceeding the size of the cavity opening.

The upper element preferably consists of a retention plate having aplurality of internally threaded apertures formed therein for releasablyreceiving the threaded portion of the stylus. The threaded apertures arespaced apart at regular intervals to enable incremental adjustment ofthe degree of anterior protrusion of the lower bite block relative tothe upper bite block.

The second element preferably consists of a guide box having an uppersurface, vertical sidewalls, and an open bottom end, the guide boxhaving a hollow area between the sidewalls comprising the internalcavity and an aperture formed on the upper surface comprising the cavityopening. The dimensions of the cavity preferably exceed the size of thestylus head and the cavity opening is laterally elongated to permit alimited degree of lateral movement of the lower bite block relative tothe stylus. The guide box further includes a base plate for releasablycovering the guide box bottom end, the base plate having an apertureformed therein to permit access to the stylus head captured within theinternal cavity.

The retention plate and the base plate each further include a pluralityof retention apertures spaced around the periphery thereof to enableacrylic to flow through the plates when the plates are initially bondedto the upper and lower bite blocks.

Preferably, the upper and lower bite blocks further include a first pairof bite pads formed on the undersurface of the upper bite block andprojecting downwardly therefrom and a second pair of bite pads formed onan upper surface of the lower bite block and projecting upwardlytherefrom for slidably engaging the first pair of bite pads. The bitepads are located in a posterior region of the bite blocks to limitclosure of the patient's jaw.

A connecting assembly for use in an intra-oral dental appliance to beworn by a patient during sleep for treatment of obstructive sleep apneaand snoring is also disclosed, the dental appliance comprising an upperbite block conforming to the patient's maxillary dentition and a lowerbite block conforming to the patient's mandibular dentition. Theconnecting assembly includes a first element securable to anundersurface of the upper bite block; a second element securable to anupper surface of the lower bite block; and an elongated connector forreleasably coupling the first and second elements together to maintainthe lower member in an anterior, protruded position relative to theupper member, the connector having an upper end which is securelyconnectable to the first element and a lower end which is looselyconnectable to the second element to permit a limited degree of lateralmovement of the lower bite block relative to the upper bite block in theprotruded position.

A method of treating snoring and obstructive sleep apnea by adjustablymaintaining a patient's mandible in a protruded position is alsodisclosed comprising the steps of (a) casting an upper bite block bytaking a mold of the patient's maxillary dentition; (b) casting a lowerbite block by taking a mold of the patient's mandibular dentition; (c)securing a first retention element to the undersurface of the upper biteblock in an anterior region thereof; (d) securing a second retentionelement to an upper surface of the lower bite block in an anteriorregion thereof, the second element comprising an upwardly projectingconnector having a lower end loosely captured within a cavity formed inthe second element; (e) determining the preferred degree of mandibularprotrusion required to alleviate the patient's sleep apnea and snoringsymptoms; and (f) releasably securing an upper end of the connector tothe first retention element at a fixed position corresponding to thepatient's preferred degree of mandibular protrusion as determined instep (e).

BRIEF DESCRIPTION OF THE DRAWINGS

In drawings which illustrate the preferred embodiment of the invention,

FIG. 1 is a schematic, side elevational view of the upper pharyngealregion of a typical patient suffering from obstructive sleep apnea orsnoring.

FIG. 2 is a schematic, side elevational view of the patient of FIG. 1fitted with the applicant's dental appliance to maintain the patient'smandible in a protruded position, thereby averting obstruction of thepharyngeal airway.

FIG. 3 is an enlarged, exploded view of the connecting assembly of theapplicant's invention for connecting the upper and lower bite blocksshown in dotted outline.

FIG. 4 is an isometric view of the applicant's dental appliance.

FIG. 5 is a top, plan view of the dental appliance of FIG. 4.

FIG. 6 is a front, elevational view of the dental appliance of FIG. 4.

FIG. 7 is an enlarged, cross-sectional view taken along section lines7—7 of FIG. 6 and looking in the direction of the arrows.

FIG. 8 is an enlarged, cross-sectional view taken along section lines8—8 of FIG. 6 and looking in the direction of the arrows.

FIG. 9 is an enlarged, cross-sectional view taken along section lines9—9 of FIG. 5 and looking in the direction of the arrows.

FIG. 10 is an enlarged, isometric view of an alternative embodiment ofthe stylus of the connecting assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 is a schematic, side elevational view of the upper pharyngealregion of a typical patient suffering from obstructive sleep apnea orsnoring. When the patient is asleep the oral cavity tissues relax andthe distal (rear) portion of the tongue 10 tends to slide rearwardlytoward the posterior pharyngeal wall 12. This may result in partial orcomplete occlusion of the pharyngeal airway 14 in the circled region 26.As the volume of airway 14 diminishes, the velocity of the air passingthe oral cavity tissues tends to increase. This may result in vibrationof the oral cavity tissues, such as the uvula 16 which is a fleshyprojection suspended from the soft palate 18 over the root of tongue 10.The vibration of these oral tissues causes the snoring sound.

FIG. 2 is a schematic, side elevational view of the individual of FIG. 1fitted with the applicant's dental appliance 20. Dental appliance 20causes the individual's mandible 22 to be moved to an anterior,protruded position relative to the upper jaw 24. This causes the dorsalsurface of the tongue 10 to move forwardly away from the posteriorpharyngeal wall 12. This in turn results in an increase in volume of thepharyngeal airway 14 as shown in the circled region 26. It has beenshown that maintaining airway 14 substantially open during sleepalleviates the undesirable symptoms associated with obstructive sleepapnea and snoring.

FIGS. 4-6 depict the preferred structure of dental appliance 20 infurther detail. Appliance 20 consists of an upper bite block 28 shapedto conform to the maxillary dentition 30 and a lower bite block 32shaped to conform to the mandibular dentition 34. Bite blocks 28, 32 arepreferably constructed from an elastomeric material. Each bite block 28,32 includes stainless steel dental wires 36 (FIG. 5) to stabilizeappliance 20 and ensure that it securely engages the wearer's teeth.

As best shown in FIGS. 4 and 6, the posterior region of each bite block28, 32 includes hard acrylic bite pads 38 which provide a stop to theclosure of the jaw and which support the wearer's tempromandibular jointas discussed further below.

As shown best in FIGS. 3 and 9, bite blocks 28, 32 are united in ananterior region of appliance 20 by means of a connecting assemblygenerally designated 40. Assembly 40 includes a maxillary retentionplate 42 which is bonded to upper bite block 28 in the anterior palatalregion behind the central incisors and a mandibular guide box assembly44 which is bonded to an anterior region of lower bite block 32.Retention plate 42 and guide box assembly 44 are preferably bonded torespective bite blocks 28,32 with heat-cureable dental acrylic.Retention plate 42 and guide box assembly 44 are connected by means of astylus 46 as described further below. Stylus 46 preferably comprises athreaded portion 47 and an enlarged head 48.

Guide box assembly 44 consists of a guide box 50 having an elongatedaperture 52 formed on its upper surface and a milled-out cavity 54formed beneath aperture 50. Assembly 44 also includes a base plate 56which may be releasably fastened to guide box 50 with screws 58. Screws58 extend through apertures 60 formed in plate 56 and are received ininternally threaded apertures 62 formed on either side of guide box 50which are alignable with apertures 60 (FIGS. 3 and 9).

As shown best in FIG. 8, the elongated guide box aperture 52 ispreferably kidney-shaped to correspond to the natural range of motion ofthe patient's jaw. Guide box 50 is positioned so that the convexcurvature of aperture 52 faces forwardly.

As best shown in FIG. 3, the threaded portion 47 of stylus 46 isinserted through guide box aperture 52 before guide box 50 and baseplate 56 are fastened together as aforesaid. Since the diameter of thestylus head 48 is larger than aperture 52, the stylus head 48 iseffectively captured within the cavity 54 formed in guide box 50. Cavity54 is sufficiently large to permit stylus head 48 to move vertically andlaterally to a limited extent.

FIG. 10 illustrates an alternative embodiment of stylus 46. In thisembodiment, only an end portion 47 of the stylus shaft is threaded. Theremainder of the shaft is of a larger diameter than threaded portion 47and is smooth and continuous. This ensures that the main body of theshaft will slide freely against the edge of guide box aperture 52 duringnocturnal jaw movements.

Stylus 46 may be manufactured in different lengths to accomodatedifferent dental configurations. The referred overall lengths of stylus46 vary between 6.8-9.8 mm.

Base plate 56 has a central aperture 64 to allow access to stylus head48 (FIG. 9). Accordingly, stylus 46 can be manually turned using ascrewdriver or some other suitable tool after guide box 50 and baseplate 56 have been fastened together.

Base plate 56 also includes a plurality of countersunk, spaced-apartretention apertures 66. Retention apertures 66 are provided to allowdental acrylic to flow upwardly through base plate 56 to facilitatebonding of guide box assembly 44 to the lower bite block 32. Apertures66 are countersunk to increase the surface area available for bonding.Preferably, the base plate 56 is larger than guide box 50 so that thedental acrylic flowing through retention apertures 66 will surround theperimeter of guide box 50, as best shown in FIG. 7.

As best shown in FIGS. 3, 4 and 7 , maxillary retention plate 42includes a series of internally threaded apertures 68 which are spacedapart at regular intervals. Apertures 68 are provided for receiving thethreaded portion 47 of stylus 46. Maxillary retention plate alsoincludes a plurality of retention apertures 66 to allow the acrylic toflow through plate 42 to facilitate its bonding to upper bite block 28.

Preferably maxillary retention plate 40 and guide box assembly 44 areconstructed from commercially pure titanium or some other metal which isnon-reactive with oral fluids. Stylus 46 and screws 58 are preferablyfabricated from titanium or stainless steel.

Dental appliance 20 is custom-fitted to suit the requirements of eachindividual patient. Usually the first step in the fitting procedure isfor the dentist or physician to assess the natural range of motion ofthe patient's jaw and the likely degree of pharyngeal occlusion. Thismay be determined by physical examinations, sleep studies, x-rays andthe like.

Molds of the patient's existing maxillary and mandibular dentition 30,34 are then taken to enable casting of U-shaped bite blocks 28, 32. Asindicated above, bite blocks 28, 32 are preferably formed of anelastomeric material. Dental wires 36 are embedded in bite blocks 28, 32to provide structural stability. Opposing pairs of bite pads 38 areformed on the undersurface of upper bite block 28 and the upper surfaceof lower bite block 32 in a posterior region of appliance 20 (FIGS. 3and 5). Bite pads 38 are constructed from hard dental acrylic and areprovided to limit closure of the patient's jaw and prevent overeruptionof the posterior teeth.

After bite blocks 28, 32 have been fabricated as aforesaid, they areunited by means of connector assembly 40 (FIG. 3). Guide box 44 andstylus 46 of assembly 40 are loosely coupled together as described aboveso that the threaded portion 47 of stylus 46 protrudes upwardly throughthe elongated aperture 52 formed in guide box 50 (FIG. 3).

Retention plate 42 is bonded to the undersurface of upper bite block 28and guide box assembly 44 is bonded to the upper surface of bite block32 by means of heat-cureable dental acrylic. The soft acrylic flowsthrough retention apertures 66 formed on retention plate 42 and baseplate 56 to ensure that connecting assembly 40 is securely set in placeas the acrylic hardens. As explained above, retention apertures 66 arecountersunk to increase the surface area available for bonding to thedental acrylic.

After dental appliance 20 has been fabricated as described above, biteblocks 28, 32 are releasably coupled together by inserting the threadedportion 47 of stylus 46, which extends upwardly from guide box 50, intoone of the mating apertures 68 formed in maxillary retention plate 42(FIGS. 3, 7 and 9). Apertures 68 are spaced approximately 0.5 mm apartto allow the dentist or physician to make small adjustments in therelative position of bite blocks 28, 32 and hence the degree of anteriorprotrusion of the patient's mandible 22. Preferably apertures 68 shouldbe spaced to allow for a total adjustment range of approximately 7 mm.The inferior position of mandible 22 (i.e. the degree of opening of thejaw) may also be incrementally adjusted by varying the extent to whichstylus 46 is screwed within a selected aperture 68. Stylus 46 may beturned with a screwdriver or other suitable tool insertable through baseplate aperture 64 to engage stylus head 48.

In practice, appliance 20 is easily insertable within the mouth of apatient for wear during sleep. Appliance 20 is initially adjusted toadvance mandible 22 between 25% and 75% of the patient's maximumprotrusive capability. Typically approximately 5-8 millimeters ofmandibular protrusion and approximately 4-6 millimeters of inferioropening are initially provided (FIG. 2). This is in contrast to someprior dental appliances where an inferior opening in the range of 10-20millimeters is recommended. The inventor's studies suggest that in manypatients the tongue 10 has a greater tendency to slide posteriorly asthe degree of jaw opening increases. Displacement of thetempromandibular joint is also more likely if the jaw is fixed in a wideopen position for long periods of time. Accordingly, dental appliance 20is set to open the jaw the minimum amount possible while still allowingthe patient to breathe comfortably through the mouth.

Opposed bite pads 38 formed on bite blocks 28, 32 provide a stop tocomplete closure of the jaw as best shown in FIGS. 4 and 6. Thisprevents overeruption of the posterior teeth during the wearing ofappliance 20 and provides support to the tempromandibular joint andassociated ligaments and muscles.

After the patient has been fitted with dental appliance 20 he or she iscarefully monitored to determine if further adjustments are required.For example, if the patient's snoring or apnea episodes have not beencompletely eliminated, then the degree of mandibular protrusion may beincrementally increased by unscrewing stylus 46 from its initialsetting, advancing lower bite block 32 forwardly, and inserting stylus46 into an adjacent aperture 68 formed on maxillary retention plate 42(FIG. 7). The degree of inferior opening of the mandible 22 can also bereadily adjusted to suit the needs of a particular patient by alteringthe extent to which the threaded portion 47 of stylus 46 is screwedwithin a selected aperture 68. If the patient experiences discomfortfrom wearing appliance 20, then the dentist or physician can readilyadjust the lower bite block 28 to a more retruded and/or a less inferiorposition.

A key feature of the applicant's invention is that connecting assembly40 allows a limited degree of lateral movement of the patient's mandible20 relative to the upper jaw 24 while still maintaining mandible 20 inthe preferred protruded position. While the upper threaded portion 47 ofstylus 46 is fixed in a selected aperture 68 formed in maxillaryretention plate 42, the stylus head 48 is not fixed relative to lowerbite block 32. Rather, stylus head 48 is loosely captured within cavity54 formed in guide box 50, as best shown in FIGS. 7-9. This allows lowerbite block 32 and hence mandible 22 to travel in a lateral excursionrelative to stylus 46 (i.e. in the direction of the arrows shown inFIGS. 6, 8 and 9). The extent of lateral travel of mandible 22 isrestricted by the size of aperture 52 formed on the upper surface ofguide box 50 and also the size of guide box cavity 54 (FIG. 8).

As best shown in FIGS. 3 and 8 and as discussed above, guide boxaperture 52 is preferably kidney-shaped to correspond to the naturalrange of motion of the patient's jaw joint. In one embodiment of theinvention, the size and shape of aperture 52 could be customized to suitthe anatomy of each particular patient, such as by performing gothicarch tracings to determine the natural range of motion of the patient'sjaw anatomy.

Prior art intra-oral devices which maintain mandible 22 in a fixed,protruded position can lead to serious side effects, particularly inpatients prone to nocturnal bruxism (teeth grinding). Such prior artdevices may result in displacement or aggravation of the patient'stempromandibular joint and associated muscles and ligaments. Theapplicant's dental appliance 20 effectively overcomes this problem byallowing a predetermined degree of lateral movement of mandible 22 inthe protruded position, while still maintaining acceptable airwaypatency.

As will be apparent to those skilled in the art in the light of theforegoing disclosure, many alterations and modifications are possible inthe practice of this invention without departing from the spirit orscope thereof. For example, more than one connecting assembly 40 couldbe provided. Further, the connecting assembly or assemblies 40 could bemounted in a posterior rather than an anterior region of dentalappliance 20. In another alternative embodiment, guide box assembly 44could be inverted so that elongate aperture 52 is formed on a top platecovering the open upper end of a guide box defining internal cavity 54.Other equivalent means for loosely coupling stylus 46 to lower biteblock 32 may also be envisaged. Accordingly, the scope of the inventionis to be construed in accordance with the substance defined by thefollowing claims.

What is claimed is:
 1. A device for improving the breathing of a usercomprising: an upper arch adapted to receive at least some of the user'supper teeth; a lower arch adapted to receive at least some of the user'slower teeth; and a connector adjustably coupling the lower arch to theupper arch, the connector operable to adjust the lower arch forwardlyrelative to the upper arch to maintain the lower jaw of the user in aprotruded, forward position, the connector operable to allow lateralmotion of the lower arch relative to the upper arch in the protruded,forward position.
 2. The device of claim 1, wherein the connector isremovably coupled to the upper arch.
 3. The device of claim 1, whereinthe connector is operable to adjustably position the lower archvertically relative to the upper arch.
 4. The device of claim 1, whereinthe connector is operable to allow the user's lower jaw to move freelyin a vertical direction relative to the upper arch.